Re: [PATCH 6/9] x86/mwait-idle: Remove the 'preferred_cstates' parameter

["Roger Pau Monné" <roger.pau@citrix.com>]

On Thu, Mar 12, 2026 at 05:56:55PM +0100, Jan Beulich wrote:
> From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
> 
> Remove the 'preferred_cstates' module parameter as it is not really useful.
> 
> The parameter currently only affects Alder Lake, where it controls C1/C1E
> preference, with C1E being the default. The parameter does not support any
> other platform. For example, Meteor Lake has a similar C1/C1E limitation,
> but the parameter does not support Meteor Lake. This indicates that the
> parameter is not very useful.
> 
> Generally, independent C1 and C1E are important for server platforms where
> low latency is key. However, they are not as important for client platforms,
> like Alder Lake, where C1E providing better energy savings is generally
> preferred.
> 
> The parameter was originally introduced for Sapphire Rapids Xeon:
> da0e58c038e6 intel_idle: add 'preferred_cstates' module argument
> 
> Later it was added to Alder Lake:
> d1cf8bbfed1ed ("intel_idle: Add AlderLake support")
> 
> But it was removed from Sapphire Rapids when firmware fixed the C1/C1E
> limitation:
> 1548fac47a114 ("intel_idle: make SPR C1 and C1E be independent")
> 
> So Alder Lake is the only platform left where this parameter has any effect.
> Remove this parameter to simplify the driver and reduce maintenance burden.
> 
> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
> Link: https://patch.msgid.link/20251215111300.132803-1-dedekind1@gmail.com
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Origin: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git a36dc37b5672
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.